A carbon quantum dot synthesizing method and its application of modifying functional water purification material

ABSTRACT

The present invention relates to the technology of material surface modification and the preparation adsorption new material, which involves the preparation of CQDs and the application of CQDs on modifying water purification function material. Firstly, the CQDs with rich functional groups and specific graphene structure has been prepared based on the low-cost biomass. Then, modified the traditional adsorbent by prepared CQDs under the in situ synthesis process. Secondly, synthesis the CQDs basic on the organic waste-water under low-temperature hydrothermal treatment process. Then, prepared the CQDs modified water purification material by collecting the CQDs under the flocculation process. This invention can be used in the widely used in the field of modification and preparation of functional materials, because of it not only gives a new method to synthesis low-cost and high performance water purification material, but also provide a new idea to treat high toxicity and refractory organic waste-water.

TECHNICAL FIELD

The invention provides a method and application of carbon quantum dotpreparation and its modified water purification function material, whichbelongs to the field of preparation of material surface modification anda kind of new water purification function materials.

BACKGROUND

As we all know, water is the most basic human resource. While 71 percentof the earth is covered by water. However the amount of fresh wateravailable for human to use is only about 0.7 percent of that. With thedevelopment of economy, environmental problems are becoming more andmore prominent. The state of China's environment indicate that 50percent of the environmental events in recent years have been related towater pollution, and the ensuing pollution incidents that waterpollution control is urgently needed. In order to control waterpollution and meet the requirements of the risk of human health and theaquatic environment, a variety of water treatment technology has beendeveloped, including the coagulation and flocculation, catalyticoxidation, membrane filtration, biological treatment, adsorption, etc.The adsorption method is the most popular method for the treatment ofpollutants in wasted water, because its advantages of thoroughtreatment, low pollutant residue concentration, and the regeneration ofadsorbent.

At present, all kinds of absorbent material has been widely applied towater treatment, inorganic materials including ionic sieve,hydrotalcite, spinel, etc., which has a good adsorption performance andselective to the target element. The ion screen materials found byformer Soviet scientist Vol 'kin showed selective adsorption of lithiumions, but the following study showed that the adsorption of lithium wassmall. Biomass material has large adsorption capacity and specificsurface area, which has been widely applied to the purification of waterquality, unmodified biomass has certain adsorption ability to the targetelement, which depends on the structure of the functional group incellulose, hemicellulose, lignin and pectin. The interior of unmodifiedbiomass is amorphous structure. Most biomass are a kind of wide-spectrumabsorbent material which have selectivity to target material. Porousbiomass adsorbent is a kind of activated carbon which activation by thebiomass substrate. BaoyuGao (shandong university) reported a modifiedbiomass adsorbent based on natural straw under the air activation whichshowed high specific surface area with good adsorption capacity.However, it's adsorption process is but a wide adsorption and wasinfluenced by the salinity of the system. The mentioned propertiesdirectly restricts the development and application the adsorbentmaterial. The modified adsorbent material obtained by modifying theoriginal adsorbent material through appropriate technical modificationcan not only overcome the limitation of the adsorption capacity oftraditional materials but also maintain its inherent advantages.Therefore, more and more technologies have been applied to theadsorption material modification including the introducing of orificesto modify its pore structure, the introducing of multi-metal skeletons,and the introducing of the crystal type and space arrangement andmagnetic materials to enhance its separation efficiency. Two physicistsat the university of Manchester, England Geim and Novoselov found thatgraphene materials also caused a strong reaction in the scientificcommunity, promote various kinds of graphene modified compositematerial, make a big breakthrough in the structure and properties of theoriginal material. Graphene composite materials have also been widelyused in many fields, such as photocatalysts, biosensors, lithium-ionbatteries and supercapacitors. This is greatly expand the applicationfield of graphene composites, at the same time provide some new ideasabout modifying traditional adsorbent. Studies have shown that thespecial properties of the graphene material depend on its special sizeand the crystal structure.

Carbon quantum dots as a new type of carbon material, not only has goodstability and biocompatibility, but also has abundant surface functionalgroups and the special structure of graphene carbon group. It was widelyused in light chemical, biological imaging and other fields because ofthe superior photoluminescence properties. However, few studies havereported its application in the modification of water qualitypurification function materials. What's more, the carbon sourceprecursor of the current carbon quantum dot material is selected as theorganic solvent of macromolecules and some biomass materials. Thereisn't any report about the application of organic wastewater directpreparation of prepare carbon quantum dots under low temperaturecarbonization. Besides, carbon quantum dots have good solubility inwater and nano structure for its purification and extraction ofdemanding. At present, the carbon quantum dots in aqueous solution areextracted by dialysis and freeze-drying, those process are not onlycomplicated and time-consuming but also need certain economic cost whichis not conducive to the production and application. Coagulationtechnology as a traditional water purification technology is widelyapplied, but there was no report about the application of coagulationtechnology to collect carbon quantum dots material. Moreover, the flcoscontains the carbon quantum dots and flocculant could be used aspotentially functional water purification materials under followingre-production process.

Therefore, the present invention aims to prepare of potentiallyfunctional water purification materials by introducing the biomass basicCQDs into the adsorbent synthesis process. This process can optimize theparticle channels and lattice vacancies of the adsorbent and formcomposite modification materials with unique lattice defects and surfaceproperties. There was no report on this modified process which can beused as new method to synthesis potentially functional compositematerials. Moreover, it also gives a new method to treat organicwaste-water and to achieve the carbon resources recycling. Therefore,the present invention not only gives new method to synthesis low-costfunctional water purification materials, but also provides a potentialmethod to treat organic waste-water.

SUMMARY

The present invention aims to provide a potential water purificationmaterials by introducing the CQDs into the adsorbent synthesizingprocess which is not only can solve insufficient of the raw material andtechnology, but also can effectively improve the adsorption performanceof the adsorbent and the treatment efficiency of the organicwaste-water.

The Present Invention has the Following Technical Solution

A preparation method of a carbon quantum dot is adopted as one of twomethods:

The first preparation method is as follows:

1) Raw biomass material were washed by the deionized water and thenfurther cut into small pieces and dry at 60° C. for 24 hours.Approximately 1-100% solid-to-liquid ratio of biomass/water mixedsuspension was prepared.

2) The mixture was then heated in a commercial oven at 100-200° C. for2-10 h or at 500-2000 W microwave reaction under the condition of 10-300min to obtain the biomass base CQDs solution with hydroxyl group andcarbonyl groups.

3) The CQDs solution was filtered and dried to get the biomass basecarbon quantum dots powder. The dried method should protect the finestructure and surface functional groups of biomass base carbon quantumdots.

The biomass material can be one or more than one of crops, fruits,discarded peel, straw, natural gum.

The Second Preparation Method is as Follows:

1) Add one appropriate amount of PEG-2000 to the organic waste-water andsupersonic dispersion to get uniform mixed liquid.

2) The mixture was then heated in a commercial oven at 100-200° C. for2-10 h or at 500-2000 W microwave reaction under the condition of 10-300min to obtain the biomass base CQDs solution with hydroxyl group andcarbonyl groups.

3) The CQDs solution was filtered and dried to get the biomass basecarbon quantum dots powder. The dried method should protect the finestructure and surface functional groups of biomass base carbon quantumdots.

The using dried method is freeze-dried method.

A Method of Preparing the CQDs Modified Composite Adsorbent is asFollows:

Carbon quantum dot powder solutions (1-100%) were prepared by DI water.Then, the CQDs solution were used in the traditional inorganic adsorbentsynthesizing process to replace the DI water and get the CQDs modifiedadsorbent. In this process, some Lattice defect or pore structure couldbe obtained by the introducing of the CQDs which are helpful to improvethe adsorbent performance.

The traditional inorganic adsorbents include molecular sieves, metaloxides, montmorillonite and mullite include, which have structure orionic memory effects.

The method of introducing CQDs includes temperature immersion, inertatmosphere, water bath, microwave or ultrasound method.

A Method of Preparing Water Purification Materials by Modified InorganicMaterials by CQDs is as Follows:

1) Add one appropriate amount of PEG-2000 to the organic waste-water andsupersonic dispersion to get uniform mixed liquid.

2) The mixture was then heated in a commercial oven at 100-200° C. for2-10 h or at 500-2000 W microwave reaction under the condition of 10-300min to obtain the biomass base CQDs solution with hydroxyl group andcarbonyl groups.

3) Add coagulant into the prepared CQDs solution and adjust the pH to7-12; then, quickly Stirring for 1-10 min, slowly stirring for 5-30 minfor 1-2 hours to get the suspension solution.

4) Filter the prepared suspension solution to obtain the CQDs modifiedcoagulant composite solids, and then calcined the coagulant to obtainthe water purification material.

The coagulant is one or more than two of iron salts, aluminum salts, andtitanium salts.

The present invention has four beneficial effects: (i) the cost of theinvention is low, and the source of biomass or organic waste water ischosen as the base material of carbon, without the need to add otheragents to prepare the carbon quantum dots of rich oxygen-containingfunctional groups. (ii) the operation is simple, only domestic oven andreaction kettle can complete, don't need special requirements such asprotective atmosphere, vacuum and high temperature, modification processwith the method of impregnation, easy to promote and mass production.(iii) the modified of adsorbent materials, not only have good adsorptionperformance, but also have abundant surface functional groups toincreases the selectivity of the target material, to reduce costs andimprove application performance. (4) it is low-cost and energy-efficientby using coagulation process to collect CQDs and to prepare the waterpurification material.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an infrared spectrogram of the carbon quantum dots that aresynthesized by the invention.

FIG. 2 is an X-ray diffraction pattern of the carbon quantum dots.

FIG. 3a is a photoelectron microscope image of a carbon quantum dot in50 nm.

FIG. 3b is a photoelectron microscope image under 10 nm for the carbonquantum dots of the invention.

FIG. 4 is a comparison curve of the adsorption performance of a biomassbase carbon quantum dot modified ion sieve material and traditionalionic sieve material for lithium elements.

FIG. 5 is a comparison curve of the adsorption performance of the boronelement with the modified water-talc material and the traditionalwater-talc material.

FIG. 6a is the X-ray photoelectron diffraction spectrum of carbonquantum dot modified titanium dioxide functional materials obtained bythe invention of coagulation recovery quantum dots.

FIG. 6b is the X-ray photoelectron diffraction spectrum of O elements inthe functional materials of the carbon quantum dots modified by theinvention of coagulation recovery quantum dots.

FIG. 6c is the X-ray photoelectron diffraction spectra of Ti elements inthe functional materials of the carbon quantum dots modified by theinvention of coagulation recovery quantum dots.

FIG. 6d is the X-ray photoelectron diffraction spectra of Ti elements inthe functional materials of the carbon quantum dots modified by theinvention of coagulation recovery quantum dots.

FIG. 7 is the degradation curve of acrylonitrile by the modification oftitanium dioxide with a carbon quantum dot.

DETAILED DESCRIPTION

The following combination of the attached drawings and technical schemefurther explains the concrete implementation of the invention.

Implementation Example 1

1) The gum were washed by the deionized water and then further cut intosmall pieces and dry at 60° C. for 24 hours. Approximately 10%solid-to-liquid ratio of gum/water mixed suspension was prepared.

2) put the gum clouding solution put in 50 mL polyethylene lining ofreaction kettle, then heated in a commercial oven at 150° C. for 5 h toobtain the gum base CQDs solution.

3) The prepared CQDs solution was filtered by the 25 microns filters toremove unreacted rubber particle and carbon particles to get the biomassbase CQDs powder. Then freeze-dried to get CQDs powder product. Thestructure information of the prepared CQDs was shown in FIG. 1-3.

4) Add one appropriate amount of CQDs powder to the DI water andsupersonic dispersion to get 1-10% CQDs solution.

5) Dissolve 11.88 g of reagent grade MnCl₂.H₂O powder in prepared CQDssolution with CQDs liquor to 200 mL to get the solution A.

6) Dissolve 12.59 g of reagent grade LiOH.H₂O powder in prepared CQDssolution with CQDs liquor to 400 mL to get the solution B.

7) In the mixing condition, the solution B is slowly added to a smoothsolution of A, and a quick stirring of over 500 rpm for 30 min to getthe brown suspension.

8) After a quick stirring of over 500 rpm, add 30% of the H₂O₂ drops of15 mL to the prepared brown suspension, and after the drop, continue tostir 2 h for more than 500 rpm, and get the brown and black suspension.

9) The black suspension was filtered and washed by DI water to get theblack filter cake.

10) wash the filter cake with deionized water for 2-3 times and dried at60-120° C. to obtain the CQDs modified lithium ionic sieve adsorbentmaterial.

Implementation Example 2

1) Add 2 mL reagent grade PEG-2000 to 15 mL organic wastewater, andultrasonic dispersing 10 min to obtain uniform liquid;

2) Put the gum clouding solution put in 50 mL polyethylene lining ofreaction kettle, then heated in a commercial oven at 150° C. for 5 h toobtain the gum base CQDs solution.

3) The prepared CQDs solution was filtered by the 25 microns filters toremove unreacted rubber particle and carbon particles to get the biomassbase CQDs powder. Then freeze-dried to get CQDs powder product. Thestructure information of the prepared CQDs was shown in FIG. 1-3.

4) Add one appropriate amount of CQDs powder to the DI water andsupersonic dispersion to get 5% CQDs solution.

5) Dissolve 18.94 g of reagent grade MgSO₄.7H₂O and 8.79 gAl₂(SO₄)₃.18H₂O powder in prepared CQDs solution with CQDs liquor to 200mL to get the solution C.

6) Dissolve 8.41 g of reagent grade NaCO₃ and 33.53 g of reagent gradeNaOH powder into DI water to get the solution D.

7) In the mixing condition, the solution D is slowly added to a smoothsolution of C, and a quick stirring of over 500 rpm for 30 min to getthe white suspension.

8) Make the prepared white suspension under 80° C. microwavecoprecipitation for 20 min, then filtered to get white filter cake.

9) wash the filter cake with deionized water for 2-3 times and dried at80° C. to obtain the CQDs modified LDHs adsorbent material.

Implementation Example 3

The adsorption of lithium by using CQDs modified ion sieve adsorbentmaterial:

1) Dissolve KCl 36.9 g, NaCl 480 g, MgCl₂.6H₂O 153 g, CaCl₂ 0.420 g,LiCl 3.01 g and H₃BO₃ 19.1 g into 2 LDI water to get the simulated saltlake water solution.

2) Add 0.1 g of the prepared CQDs modified ion sieve adsorbent materialand traditional ion sieve adsorbent material into the 100 mL simulatedsalt lake water solution, respectively. Then, stirred for some time andmeasured the concentration of lithium ions.

3) The adsorption performance of the two adsorbents were shown in FIG.4.

Implementation Example 4

The adsorption of boron by using CQDs modified LDHs material:

1) Dissolve 20 mg of reagent grade H₃BO₃ powder into 1 L DI water to getthe boron solution.

2) Add the proper amount of NaOH to adjust the solution pH to 7-8.

3) Add 200 mg of the prepared CQDs modified LDHs material andtraditional LDHs adsorbent material into the 1 L prepared boronsolution, respectively. Then, stirred for some time and measured theconcentration of lithium ions.

4) The adsorption performance of the two adsorbents on boron were shownin FIG. 5.

Implementation Example 5

Using titanium coagulation collect CQDs to prepare functional waterpurification material.

1) Add one appropriate amount of titanium sulfate to the DI water to getthe 2M titanium salt coagulant solution.

2) Add 2 ml of the prepared titanium salt coagulant to the CQDs solution(from step 2), stirring well.

3) adjust PH of the mixture solution to 8, and stir quickly for 5 min;

4) then, slow stirring for 20 min, sit for 30 min.

5) Filtered the mix solution and dried the filtercake at 100° C. to getthe CQDs modified titanium oxide A.

6) calcine the CQDs modified titanium oxide A at 450° C. for 2 h to getmodified water purification material B.

7) add 20 mg water purification material B the water purifier powderinto 100 mL acrylonitrile solution (20 mg/L), uv lighting 2 h, anddetermination of the remaining acrylonitrile concentration.

8) the X-ray photoelectron diffraction spectra of the modified waterpurification B are shown in FIG. 6;

9) the concentration of acrylonitrileis shown in FIG. 7.

1. A preparation method of a carbon quantum dot, comprising steps of: 1)washing raw biomass material by deionized water and then further cuttingthe raw biomass material into small pieces and drying the raw biomassmaterial at 60° C. for 24 hours; preparing 1-100% solid-to-liquid ratioof biomass/water mixed suspension; 2) heating the mixed suspension at100-200° C. for 2-10 hours to obtain biomass base CQDs (Carbon QuantumDots) solution with hydroxyl group and carbonyl groups; and 3) filteringand drying the biomass base CQDs solution to get biomass base carbonquantum dots powder, so as to protect fine structure and surfacefunctional groups of the biomass base carbon quantum dots.
 2. Apreparation method of a carbon quantum, comprising steps of: 1) addingamount of PEG-2000 to organic waste-water and supersonic dispersion toget uniform mixed liquid; 2) heating the uniform mixed liquid at100-200° C. for 2-10 hours or at 500-2000 W microwave reaction under acondition of 10-300 minuets to obtain biomass base CQDs (Carbon QuantumDots) solution with hydroxyl group and carbonyl groups; and 3) filteringand drying the biomass base CQDs solution to get biomass base carbonquantum dots powder, so as to protect fine structure and surfacefunctional groups of the biomass base carbon quantum dots.
 3. Thepreparation method of claim 1, wherein the raw biomass material is oneor more than one of crops, fruits, discarded peel, straw, and naturalgum.
 4. The preparation method of claim 1, wherein drying the biomassbase CQDs solution is via a freeze-dried method.
 5. A method ofpreparing adsorbent by using carbon quantum dots to prepare inorganicmaterials, comprising steps of: preparing carbon quantum dots (CQDs)solution (1-100% of solid-to-liquid ratio) by DI water (deionizedwater); and applying the CQDs solution in an inorganic adsorbentsynthesizing process to replace the DI water and get CQDs modifiedadsorbent; whereby lattice defect or pore structure are obtained byintroducing the biomass base CQDs solution which is helpful to improveadsorbent performance of the CQDs modified adsorbent.
 6. The preparationmethod of claim 1, further comprising a step of preparing adsorbent byusing carbon quantum dots to prepare the inorganic materials,comprising: preparing carbon quantum dot powder solutions (1-100% ofsolid-to-liquid ratio) by DI water (deionized water); applying thebiomass base CQDs solution in an inorganic adsorbent synthesizingprocess to replace the DI water and get CQDs modified adsorbent; wherebylattice defect or pore structure are obtained by introducing the biomassbase CQDs solution which is helpful to improve adsorbent performance ofthe CQDs modified adsorbent.
 7. The method of claim 5, wherein inorganicadsorbents in the inorganic adsorbent synthesizing process includemolecular sieves, metal oxides, montmorillonite and mullite include,which have structure or ionic memory effects; wherein introducingbiomass base CQDs solution is applied via temperature immersion, inertatmosphere, water bath, microwave or ultrasound method.
 8. The method ofclaim 6, wherein inorganic adsorbents in the inorganic adsorbentsynthesizing process include molecular sieves, metal oxides,montmorillonite and mullite include, which have structure or ionicmemory effects; wherein introducing biomass base CQDs solution isapplied via temperature immersion, inert atmosphere, water bath,microwave or ultrasound method.
 9. A method of preparing waterpurification materials by modified inorganic materials by CQDs (carbonquantum dots), comprising steps of: 1) adding amount of PEG-2000 toorganic waste-water and supersonic dispersion to get uniform mixedliquid; 2) heating the uniform mixed liquid at 100-200° C. for 2-10hours or at 500-2000 W microwave reaction under the condition of 10-300minutes to obtain biomass base CQDs solution with hydroxyl group andcarbonyl groups; 3) adding coagulant into the biomass base CQDs solutionand adjust pH of the biomass base CQDs solution to 7-12; quicklystirring the biomass base CQDs solution for 1 to 10 minutes, and thenslowly stirring the biomass base CQDs solution for 5 to 30 minutes toget a suspension solution; and 4) filtering the suspension solution toobtain CQDs modified coagulant composite solids, and then calcining theCQDs modified coagulant composite solids to obtain water purificationmaterial.
 10. The method of claim 9, wherein the CQDs modified coagulantcomposite solids is one or more than two of iron salts, aluminum salts,and titanium salts.